1. Field of the Invention
The present invention relates to a bone drill machine for surgery.
2. Description of the Prior Art
During a surgical operation, a craniotomy drill is often used to open a skull. The craniotomy drill comprises a main machine, a retarder, a locking seat and a drill bit. The main machine comprises a handle at a lower part thereof and a casing having a cylindrical accommodating part and a cylindrical electric motor at an upper part thereof. To assemble the craniotomy drill, the electric motor is placed in the chamber of the cylindrical accommodating part at the upper part of the casing, and then the electric motor is secured with screws. This structure has a large-size upper part of the casing and the whole weight of the craniotomy drill is heavy. After a period of time to use, the screws may loosen and the electric motor may slip off from the accommodation room to cause an accident during surgery.
Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.